The invention relates to a semiconductor device and a method of manufacturing a semiconductor device.
In recent years, along with high integration of semiconductor devices, various structures of semiconductor devices have been proposed in order to reduce the area of a semiconductor device. For example, transistors provided with a gate electrode in a trench part are disclosed, as documents below.
In Patent document 1 (Japanese Patent Laid-Open No. 1999-103058), there is described a following semiconductor device. In a surface of an N-type high resistive layer, a trench (a trench part) is formed. In the trench, a gate electrode is buried via a gate insulating film. It is described that, since this makes it possible to broaden the area of a channel while keeping an element area to be unchanged, ON resistance can be reduced.
Furthermore, as in following documents, a structure of stacking a plurality of contacts, that is, “a stacked contact structure” is disclosed.
In Patent Document 2 (Japanese Patent Laid-Open No. 2009-252924), there is described a semiconductor device having a following stacked contact structure. Over a first contact, second and third contacts are provided. The second contact is disposed, shifted to the left side relative to the center position of the first contact. On the other hand, the third contact is disposed, shifted to the right side relative to the center position of the first contact. It is described that, even when a concave part (what is called a seam) is generated in an upper part of the first contact, consequently, a contact resistivity anomaly or a contact failure can be avoided.
In Patent Document 3 (Japanese Patent Laid-Open No. 2005-332978) there is described a semiconductor device having a following stacked contact structure. A first contact passes vertically through a first interlayer insulating film and has a ring-like cross-sectional shape at the upper end part. A second contact passes vertically through a second interlayer insulating film provided over the first interlayer insulating film. The center part of the lower surface of the second contact is in contact with the upper surface formed into a ring-like shape in the first contact. It is described that, consequently, electric connection between stacked contacts can be realized definitely.